1. Field of the Invention
The present invention relates to a communication method and apparatus adapted to data communications among devices that are interconnected via an IEEE 1394 bus line, for example.
2. Description of the Related Art
There have been developed AV devices for mutually transmitting information through a network employing an IEEE 1394 serial data bus. When transmitting data via the foregoing bus, an isochronous transfer mode used in transmitting a relatively large volume of video data, audio data, etc. in real time and an asynchronous transfer mode used in transmitting a still image, text data, a control command, etc. in a reliable manner are available, and a specific bandwidth is used for transmission in each mode.
According to the transmission structure employing the IEEE 1394 bus, when a source device as a device for sending data, a destination device as a device for receiving the data sent from the source device, and a controller for controlling data transmission between these two devices are linked to the IEEE 1394 bus, the data is transmitted from the source device to the destination device under the control of the controller. More specifically, in case of sending video data from the source device to the destination device, the controller secures an isochronous transfer channel on the bus, and establishes a connection between the source device and destination device to enable transmission through the secured channel, after which the controller starts the transmission from the source device to the destination device.
When the data is transmitted between the source device and destination device in the above manner, a control command transmission method called AV/C command (AV/C Digital Interface Command Set) that is adapted to the audio and video devices (so-called AV devices) or the like can be used, for example. The AV/C command is disclosed in detail in the home page at http://www.1394TA.org.
Incidentally, in a network where transmission can be controlled by the conventional AV/C command, it is necessary to specify the type of information that is read out from and written to each device linked to the bus. For example, in case that data is transmitted between the foregoing source device and destination device under the control of the controller, it is necessary to pre-install a function for running an assigned job to each device linked to the bus.
When information transmitted between the devices has to be specified in advance as described above, functions realized by these devices are limited to the pre-installed functions. This is not preferable when flexibility of the data transmission on the network, expansion of the functions, etc. are concerned.
It is therefore an object of the present invention to realize transmission of various kinds of information, such as control information, among devices constituting, for example an IEEE 1394 network.
A communication method of the present invention is a communication method for allowing communications among devices linked to a predetermined network, wherein: at least one of the devices linked to the network is provided with a storage region to/from which data is written/read out when a predetermined command is transmitted from any other device on the network; and data transmission throughout the network is allowed by using the storage region.
A communication apparatus of the present invention is a communication apparatus linked to a predetermined network, comprising:
control means for controlling communications with any other device within the network; and a storage unit to/from which data is written/read out at a command from any other device within the network judged by the control means.
By adapting the above inventions, arbitrary data can be written/read out to/from a predetermined storage region in at least one network-linked device under the control of the other devices. Thus, information related to an arbitrary function can be written to the storage region by the other devices, or the information on the function needed by the other devices can be read out from the storage region.